The present invention represents an improvement over the type of apparatus which is the subject of U.S. Pat. No. 5,069,018 with the application for which this application was co-pending. The apparatus described in that patent includes a base with a stationary heating hood. A rectangular stationary packaging table is mounted on the base and extends laterally outwardly from beneath the heating hood. A movable rectangular sealing frame is mounted on the base beneath the heating hood and over the packaging table. This sealing frame includes a top frame portion and a bottom frame portion which are hingedly connected together. The top frame portion is hingedly movable between an open position and a closed position relative to the bottom frame portion. In the open position, the top frame portion is pivoted away from the bottom frame portion to allow loading of a sheet of plastic film between the top frame portion and the bottom frame portion. Also, movement of the top frame portion into the open position allows removal of the final package product from the machine. When the top frame portion is moved into the closed position, the top frame portion is placed against the bottom frame portion to hold the plastic sheet taut between the two frame portions. The sealing frame is connected to the base and can be moved to a heating position wherein the sealing frame and plastic sheet held by the frame are positioned below the heating hood. The sealing frame can also be moved to a sealing position, wherein the sealing frame and the plastic sheet are positioned on the packaging table where a vacuum condition may be created to draw the heated plastic sheet over the article to be packaged against the underlying card on the table.
Providing a heating hood above the film in its heating position is typical of the prior art, such as has been cited and discussed during the prosecution of the earlier patent. This may require that the heating elements in the heating hood be maintained in continuous energized condition, particularly where the interval between exposures of plastic film sheets to the heating element may be relatively brief and the desired time of exposure likewise may be brief. However, when the heating element is continually energized, this is not only wasteful of electrical energy (and can also be expensive), but in certain work environments, such as an unair-conditioned plant in the summer, can greatly increase discomfort for the operator of the machine. Also, since the heating element radiates downwardly below the hood, considerable heat energy is required.